Acute myocardial infarct
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This micrograph shows a transmural transverse section of the left ventricle. At low magnification there is an irregular contoured band of blue (basophilic) material that surrounds a pink/red core of dead myocardium. The subendocardium (top) shows viable myocytes which receive oxygen and nutrients from the chamber of the left ventricle, and therefore survive the lack of flow during a coronary artery occlusion. The green rectangle in the subendocardium shows that after a few layers of normal looking myocytes, there is a layer of myocytes with pale sarcoplasm which indicated colliquative myocytolysis (or hydropic change). At lower magnification there is a gradient of normal myocytes on the left side of the field where the myocytes show normal nuclei, and as you examine the myocardium closer to the blue band of tissue, there are small veins and arterioles thrombosed. The large blue band of debris corresponds to a front of polymorphonuclear leukocytes which have undergone extensive karyorrhexis. (See the green rectangle in the border of karyorrhectic cells). The core of tissue inside the large blue front of karyorrhexis shows eosinophilic (pink) cells devoid of any nuclei, which correspond to dead myocytes and dead capillary endothelial cells. The extensive karyorrhexis occurs between 72-96 hours after the onset of the infarct. The white whole in the middle of the section is an artifact of histologic sectioning. The transmural nature of this infarct is accompanied by a pericardial inflammatory response (Green rectangle near the epicardial coronary artery).
